Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
DTC Descriptors
DTC P1085: Fuel Supply Pump Protection/Fuel Supply Pump Exchange, Fuel Pressure Regulator 2 PerformanceDTC P1295: High Pressure Fuel Supply Pump Performance/Fuel Pressure Regulator 2 Performance
Diagnostic Fault Information
Circuit | Short to Ground | Open | Short to Voltage |
|---|---|---|---|
Fuel Rail Pressure Sensor 5-Volt Reference | P0192, P0642 | P0192 | -- |
Fuel Rail Pressure Sensor Signal Circuit 1 | P0192 | P0193 | P0193 |
Fuel Rail Pressure Sensor Signal Circuit 2 | P0192 | P0193 | P0193 |
Fuel Rail Pressure Sensor Signal Circuit 1 and 2 | P0192 | P0193 | P0193 |
Fuel Rail Pressure Sensor Ground Circuit | -- | P0193 | -- |
Typical Scan Tool Data
Circuit | Short to Ground | Open | Short to Voltage |
|---|---|---|---|
Operating Conditions: Engine Running Parameter Normal Range: 25 MPa | |||
Fuel Rail Pressure Sensor 5-Volt Reference Circuit | 0.0 MPa | 0.0 MPa | -- |
Fuel Rail Pressure Sensor Signal Circuit 1 | 0.0 MPa | 246.6 MPa | 246.6 MPa |
Fuel Rail Pressure Sensor Signal Circuit 2 | 0.0 MPa | 246.6 MPa | 246.6 MPa |
Fuel Rail Pressure Sensor Signal Circuit 1 and 2 | 0.0 MPa | 246.6 MPa | 246.6 MPa |
Fuel Rail Pressure Sensor Ground Circuit | -- | 246.6 MPa | -- |
Circuit/System Description
The common rail fuel system is comprised of two fuel pressure sections: a suction side between the fuel tank and the fuel supply pump and a high-pressure side between the fuel supply pump and the fuel injectors. Fuel is drawn from the fuel tank via a feed pump, then pumped into the fuel rail by two plungers, all of which are internal to the fuel supply pump. This high pressure is regulated by the engine control module (ECM) using the fuel rail pressure (FRP) regulator dependant upon values from the FRP sensor attached to the fuel rail. In case of fuel rail overpressure, a pressure limiter valve threaded into the fuel rail will open to release overpressure and return fuel back to the fuel tank.
Conditions for Running the DTC
P1085
| • | DTCs P0089, P0091, P0092, P0192, P0193, P0642 and P0643 are not set. |
| • | The engine is running. |
| • | The battery voltage is between 10-16 volts. |
P1295
| • | DTCs P0016, P0089, P0091, P0092, P0192, P0193, P0201, P0202, P0203, P0204, P0205, P0206, P0335, P0336, P0602, P0642, P0643, P0652, P0653, P1293, P2146, P2147, P2148, P2149, P2150, P2151, P2161, P2164, P2167, P2170, P2173, P2176, and P268A are not set. |
| • | The desired fuel rail pressure does not vary more than 2 MPa. |
| • | The fuel injection quantity does not vary more than 2 mm³. |
Conditions for Setting the DTC
P1085
| • | The ECM detects that the actual fuel rail pressure is more than 197 MPa for longer than 35 seconds. |
| OR |
| • | The ECM detects that the actual fuel rail pressure is more than 230 MPa for longer than 1 second. |
P1295
The ECM detects that the oscillation of fuel feed quantity is more than a threshold, and oscillations have occurred continuously for 1,000 times, 2 tests per crankshaft revolution.
Action Taken When the DTC Sets
| • | DTCs P1085 and P1295 are Type D DTCs. |
| • | The malfunction indicator lamp (MIL) is not illuminated. |
| • | The ECM records Freeze Frame data. |
Conditions for Clearing the DTC
| • | DTCs P1085 and P1295 are Type D DTCs. |
| • | The control module turns OFF the MIL after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
Diagnostic Aids
Inspect for any recent engine mechanical repairs. An incorrectly installed fuel rail pressure (FRP) regulator will cause this DTC to set.
Reference Information
Schematic Reference
Connector End View Reference
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Special Tools
| • | EN-47667 Fuel Pressure/Vacuum Gage Adapter |
| • | J 44638 Vacuum Gage |
Circuit/System Verification
Verify the integrity of the fuel system fuel rail pressure (FRP) regulator by inspecting for the following conditions:
| • | Damaged components |
| • | Loose or improper installation |
Circuit/System Testing
Important: You must perform Circuit/System Verification before proceeding with Circuit/System Testing.
- Start the engine and operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the freeze Frame/Failure Records.
- Observe the Actual Fuel Pressure parameter with a scan tool. The actual pressure should be 0 MPa with the engine not running at operating temperature.
- Observe the Actual Fuel Pressure parameter with a scan tool. The actual pressure should be 30 MPa with the engine idling at operating temperature.
- Change the fuel pressure with a scan tool, incrementing through the entire fuel pressure range. The fuel pressure should increment and stabilize through the entire fuel pressure range with the actual desired fuel pressure within 2 MPa of each other.
- Observe the Actual Fuel Pressure parameter with a scan tool. The actual pressure should be 197 MPa with the wide open throttle (WOT) at operating temperature.
- Connect the suction side of the EN-47667 with the J 44638 assembly in series with the filter housing and the disconnected fuel hose. Bleed the fuel system by priming the priming pump until it becomes firm, then crank over the engine for a maximum of 5 seconds. Repeat as necessary until the engine starts.
- Let the engine run at idle for at least 1 minute. Monitor the fuel vacuum/pressure gage while holding the engine speed higher than 2,500 RPM for a minimum of 1 minute.
- Observe the fuel vacuum/pressure with a pressure gage. The vacuum/pressure gage ever indicate a larger vacuum than 5 in Hg.
- Test the injector for injector balance test with a scan tool
| ⇒ | If the pressure difference between the actual and desired pressure are more than 2 MPa, replace the fuel rail pressure sensor. |
| ⇒ | If the pressure difference between the actual and desired pressure are more than 2 MPa, replace the fuel pressure regulator. |
| ⇒ | If the pressure ever exceeds the specified value, replace the FRP sensor. |
| ⇒ | If vacuum/pressure gage ever indicate a larger vacuum than the specified amount during the test, repair or replace the fuel line/fuel filter/fuel tank. |
| ⇒ | If engine noise does not change, replace the fuel injector. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for engine control module (ECM) replacement, setup, and programming |
